1. Field of the Invention
This invention relates to a resistance-capacitance (R-C) network, and more particularly, to an R-C network comprising first and second layers of both dielectric and low-resistance electrically conductive material arranged face-to-face adjacent each other in an alternating sequence, and having at least three terminals.
2. Descripton of the Prior Art
Rolled type capacitors composed of two dielectric strips each bearing a metallized coating on one side thereof, which coatings can be continuous or machined into various configurations of interconnected sectional areas, and arranged alternately one above the other before being wound about a common axis, are known. See, for example, U.S. Pat. No. 2,216,558, issued to A. Ortlieb on Oct. 1, 1940, and U.S. Pat. Nos. 2,683,792 and 2,716,180, issued to W. Dubilier on July 13, 1954 and Aug. 23, 1955, respectively. These capacitors have been used individually in circuits or in combination with discrete resistor and/or inductor elements to form a network.
In more recent years, the miniaturization of both circuits and devices, such as, for example, relay coils, has created an interest in also fabricating various R-C networks which have a minimal physical size to enable the networks to, inter alia, be connected between closely spaced terminals and/or with devices mounted within metal containers or cans for shielding purposes. One solution to miniaturizing an R-C network is disclosed in U.S. Pat. No. 3,443,311, issued to W. Worobey on May 13, 1969. There, a thin film distributed R-C network is formed by depositing a layer of a film-forming metal of the type whose oxides are known to be excellent dielectric materials on a cleansed substrate by condensation techniques, anodizing the deposited film-forming metal surface to form an anodic oxide layer, depositing a layer of low-density tantalum upon the oxide layer, and generating a desired resistor pattern in the low-density tantalum layer by conventional photoengraving techniques.
Another solution to miniaturizing R-C networks is found in U.S. Pat. No. 3,786,322, issued to D. R. Brown et al. on Jan. 15, 1974, where the broad concept of using a rolled type capacitor to produce the R-C network was disclosed. There, two strips of dielectric material having a contiguous layer of metal on one side thereof are wound while each metallic layer is machined, preferably by a laser beam, to form an elongated conductive path extending back land forth lengthwise along the associated strip in a serpentine fashion so that is comes to exhibit a resistance value of R between its ends. A separate electrical contact is made with only one end of each conductive path at opposed edges of the two strips to produce a two-terminal R-C network.
Design problems are, however, encountered where more complex R-C networks are to be fabricated, such as those networks which include three or more terminals or a plurality of resistors or capacitors on one or more of the metallized layers. U.S. Pat. 3,859,592, issued to H. Kessler on Jan. 7, 1975 provides one solution for overcoming the above-mentioned problems. There, electrical R-C elements are formed of two or more insulating foils and layers of electrically conductive materials arranged alternately to form a stack wherein at least one of the layers of conductive materials is a high resistance layer for forming the resistive elements, and alternate layers are staggered with respect to one another. Various configurations of R-C elements, having two or more connections thereto, are disclosed as possible by providing incisions in the stack and by the proper selection of the stacked layers and the number and length of incisions into the formed stack.
The problem, therefore, still remains of providing R-C networks comprising three or more terminals which only use the more economical low-resistance layers, and which can be economically mass produced without first forming a stack of layered insulating and electrically conductive foils where the stack arrangement is dependent on the desired R-C network configuration, and then attempting to maintain the stack orientation during the winding process after incisions have been made therein. An additional problem with the prior art is the need to fabricate a wound R-C network in which it is possible to control and minimize the distributed capacitance in the network elements.